Apparatus and method of preparing and delivering a fluid mixture using direct proppant injection

ABSTRACT

An apparatus and method for preparing and delivering a fluid mixture. The apparatus including a high pressure differential solids feeder assembly and a pressurized mixing apparatus. The feeder assembly is coupled to a proppant storage vessel at ambient pressure and receives a continuous unpressurized proppant output flow from the proppant storage vessel. The feeder assembly is configured to output a continuous pressurized proppant output flow of sufficient mass to achieve continuous operation of the apparatus in an uninterrupted episode for an individual fracture stage. The pressurized mixing apparatus is coupled to the feeder assembly and in fluidic communication with the continuous pressurized proppant output flow and a continuous pressurized fracturing fluid flow. The pressurized mixing apparatus is configured to output a continuous flow of a pressurized fluid mixture of a sufficient volume and mass to achieve continuous operation of the apparatus in an uninterrupted episode for the individual fracture stage.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.13/689,873, filed Nov. 30, 2012 and is herein incorporated in itsentirety by reference.

BACKGROUND

Embodiments disclosed herein relate generally to an apparatus and methodof delivering a fluid mixture (i.e., slurry) into a wellbore in anuninterrupted episode for each fracture stage design.

Hydraulic stimulation or fracturing, commonly known as hydrofracking, orsimply fracturing, is a technique used to release petroleum, natural gasor other substances for extraction from underground reservoir rockformations. A wellbore is drilled into the reservoir rock formation, anda treatment fluid is pumped which causes fractures and allows for therelease of trapped substances produced from these subterranean naturalreservoirs. Current wellbore fracturing systems utilize a processwherein a slurry of a fracturing fluid and a proppant (e.g. sand) iscreated and then pumped into the well at high pressure. When water-basedfracturing fluids are used, the proppant, water and appropriatechemicals can be mixed at atmospheric pressure and then pumped up to ahigher pressure for injection into the well.

This type of hydraulic stimulation, utilizing water-based fracturingfluids, is usually undertaken in multiple fracture stages or episodes.Stimulation of each individual fracture stage utilizes a specific fluidvolume and proppant mass per stage and, due to the ability to operateand hold these materials under ambient conditions, each fracture stageis able to be conducted in one uninterrupted episode. Subsequent tocompletion of one fracture stage, a subsequent fracture stage iscommenced utilizing another specific fluid volume and proppant mass tocomprise the slurry, and the process repeats.

At present, the desire in the industry is to stimulate using fluidsother than water, and more specifically liquefied or dense phasesupercritical gases, but maintaining the same fluid volumes and proppantmass per fracture stage that is used for today's known water stimulationmethods. With the use of these alternate fluids, the stimulation of eachindividual fracture stage is still desirably sought to be accomplishedin an uninterrupted episode for each fracture stage. However, whenfluids other than water (e.g. liquid CO₂ or liquid propane) are used asthe fracturing fluid, these fluids must be kept at a sufficient pressurethroughout the hydraulic fracturing system to avoid undesiredvaporization. As a result, the blending of these fracturing fluids withproppant, chemicals, etc., to form the fracturing slurry, must also beaccomplished while the fluids are kept under a sufficiently highpressure. Current pressurized blenders, or mixing apparatus exist, forthis purpose but with limitations.

Known pressurized blenders capable of blending these vaporizingfracturing fluids with the proppant at a suitably high pressuretypically utilize a pressurized proppant storage vessel to feed andmeter the proppant into the pressurized fracturing fluid. These knownpressurized blenders require pre-loading with the entire desired mass ofproppant to be utilized during a given fracture stage. After loading,the entire mass of proppant is maintained under pressure within theblender. The pressurized proppant storage vessels are typically singlelock hopper configurations having a capacity in the range of 20-40 tonsof proppant (e.g., sand). However, typical fracture stage designs employ125,000-250,000 lbs. or more of proppant for each stage of fracturing.Due to volume limitations, a single known pressurized lock hopper andpressurized blender assembly would only able to pump a fraction of thecomplete fracture stage design. To provide the required large proppantmass, multiple lock hopper configurations may be utilized to deliver thedesired fracture stage design with proppant and additional fracturingfluids.

In addition, the limited volume capacity of known pressurized proppantstorage vessel systems provides for limited amounts of proppant to beblended with the fracturing fluid. If the fracturing design requiresmore sand, then multiple pressurized proppant storage vessels must beused. This adds to the complexity and capital expenditures of thefracturing system. In addition, known pressurized blenders require anundesirably long elapsed time to reload them with proppant for the nextfracture stage. In some instances, some pressurized blender operationsrequire the blender unit be moved off-site to another location for thepurpose of reloading with proppant, also requiring an undesirably longtime and potentially adding to the truck traffic associated withfracturing operations. In many instances, the limited capacity requiresspecialized logistics and on-pad (or off-pad) proppant handlingequipment to be used in conjunction with the pressurized proppantstorage vessel system.

Accordingly, there is a need for an improved pumping system and methodfor delivering the alternate fracturing fluids (e.g., liquid CO₂ orliquid propane), and more particularly a fracturing slurry, into awellbore that will enable the blending and pumping of essentiallyunlimited quantities on an uninterrupted basis of proppant and alternatefracturing fluid to form the fluid mixture. The ability to deliverunlimited quantities will provide for continuous operation of thepressurized blender and sand feeding equipment in an uninterruptedepisode throughout each fracture stage, maintain the same desired totalfluid volume and proppant mass for each individual fracture stage ineach uninterrupted episode, enable fracture plans to be based uponreservoir stimulation requirements without imposing equipmentconstraints, and therefore providing overall a more efficient hydraulicfracturing system.

BRIEF SUMMARY

These and other shortcomings of the prior art are addressed by thepresent disclosure, which provides an apparatus and method of preparingand delivering a fluid mixture using direct proppant injection to apressurized mixing apparatus.

In accordance with an embodiment, provided is an apparatus for preparingand delivering a fluid mixture. The apparatus includes a high pressuredifferential solids feeder assembly coupled to a proppant storage vesselat an ambient pressure and a pressurized mixing apparatus coupled to thehigh pressure differential solids feeder assembly. The high pressuredifferential solids feeder assembly includes a proppant inlet in fluidiccommunication with a proppant flow at the ambient pressure. The highpressure differential solids feeder assembly is configured to output acontinuous pressurized proppant output flow of a sufficient mass toachieve continuous operation of the apparatus in an uninterruptedepisode for an individual fracture stage. The continuous pressurizedproppant output flow is output at a mixing pressure, wherein the mixingpressure is greater than the ambient pressure. The pressurized mixingapparatus is coupled to the high pressure differential solids feederassembly. The pressurized mixing apparatus includes at least one inletin fluidic communication with the continuous pressurized proppant outputflow and a continuous pressurized fracturing fluid flow. The pressurizedmixing apparatus is configured to mix the continuous pressurizedproppant output flow and the continuous pressurized fracturing fluidflow therein and output a continuous flow of a pressurized fluid mixtureof proppant and fracturing fluid of a sufficient volume and mass toachieve continuous operation of the apparatus in an uninterruptedepisode for the individual fracture stage. The continuous flow of thepressurized fluid mixture of proppant and fracturing fluid is output ator above the mixing pressure.

In accordance with another embodiment, provided is an apparatus forpreparing and delivering a fluid mixture. The apparatus includes aproppant storage vessel, a high pressure differential solids feederassembly, a fracturing fluid storage vessel, a pressurized mixingapparatus and a pump assembly. The proppant storage vessel is configuredto contain therein a proppant material and output a proppant output flowat ambient pressure. The high pressure differential solids feederassembly is coupled to the proppant storage vessel. The high pressuredifferential solids feeder assembly includes a proppant inlet in fluidiccommunication with the proppant output flow. The high pressuredifferential solids feeder assembly is configured to output a continuouspressurized proppant output flow of a sufficient mass to achievecontinuous operation of the apparatus in an uninterrupted episode for anindividual fracture stage. The continuous pressurized proppant outputflow is output at a mixing pressure, wherein the mixing pressure isgreater than the ambient pressure. The fracturing fluid storage vesselis configured to contain therein a fracturing fluid and output acontinuous pressurized fracturing fluid output flow at a mixingpressure, wherein the fracture mixing pressure is greater than theambient pressure. The pressurized mixing apparatus is coupled to thehigh pressure differential solids feeder assembly. The pressurizedmixing apparatus including at least one inlet in fluidic communicationwith the continuous pressurized proppant output flow and the continuouspressurized fracturing fluid flow. The pressurized mixing apparatus isconfigured to mix the continuous pressurized proppant output flow andthe continuous pressurized fracturing fluid flow therein and output acontinuous flow of a pressurized fluid mixture of proppant andfracturing fluid of a sufficient volume and mass to achieve continuousoperation of the apparatus in an uninterrupted episode for theindividual fracture stage. The continuous flow of the pressurized fluidmixture of proppant and fracturing fluid is output at or above themixing pressure. The pump assembly is coupled to the pressurized mixingchamber and configured to deliver the pressurized fluid mixture thereinto a downstream component at an injection pressure, wherein theinjection pressure is greater than the mixing pressure.

In accordance with yet another embodiment, provided is a method ofpreparing and delivering a fluid mixture. The method including providinga continuous proppant output flow at ambient pressure into a highpressure differential solids feeder assembly configured to output acontinuous pressurized proppant output flow of a sufficient mass toachieve continuous operation of the apparatus in an uninterruptedepisode for an individual fracture stage, wherein the continuouspressurized proppant output flow is output at a mixing pressure, whereinthe mixing pressure is greater than the ambient pressure; inputting thecontinuous pressurized proppant output flow and a continuous pressurizedfracture fluid output flow at the mixing pressure and of a sufficientvolume to achieve continuous operation of the apparatus in anuninterrupted episode for an individual fracture stage, into apressurized mixing apparatus; and mixing the continuous pressurizedproppant output flow and the continuous pressurized fracturing fluidoutput flow therein the pressurized mixing apparatus and outputting acontinuous pressurized flow of a fluid mixture of proppant andfracturing fluid of a sufficient volume and mass to achieve continuousoperation of the apparatus in an uninterrupted episode for theindividual fracture stage, wherein the continuous flow of thepressurized fluid mixture of proppant and fracturing fluid is output ator above the mixing pressure.

Other objects and advantages of the present disclosure will becomeapparent upon reading the following detailed description and theappended claims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The above and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein

FIG. 1 is a schematic diagram of an apparatus for delivering a fluidmixture using a high pressure differential solids feeder assembly fordirect proppant injection to a pressurized mixing apparatus constructedin accordance with an embodiment;

FIG. 2 is a schematic diagram of a portion of the apparatus of FIG. 1including a feeder assembly and pressurized mixing apparatus constructedin accordance with an embodiment;

FIG. 3 is a schematic diagram of an apparatus for delivering a fluidmixture using a Continuous solid feed pump assembly for direct proppantinjection to a pressurized mixing apparatus constructed in accordancewith another embodiment;

FIG. 4 is a schematic diagram of an apparatus for delivering a fluidmixture using a eductor pump assembly direct proppant injection to apressurized mixing apparatus constructed in accordance with stillanother embodiment;

FIG. 5 is a schematic diagram of an apparatus for delivering a fluidmixture using a pressurized rotary positive displacement pump assemblyfor direct proppant injection to a pressurized mixing apparatusconstructed in accordance with still another embodiment; and

FIG. 6 is a schematic block diagram of a method of delivering a fluidmixture using a direct proppant injection to a pressurized mixingapparatus constructed in accordance with still another embodiment.

DETAILED DESCRIPTION

This disclosure will be described for the purposes of illustration onlyin connection with certain embodiments; however, it is to be understoodthat other objects and advantages of the present disclosure will be madeapparent by the following description of the drawings according to thedisclosure. While preferred embodiments are disclosed, they are notintended to be limiting. Rather, the general principles set forth hereinare considered to be merely illustrative of the scope of the presentdisclosure and it is to be further understood that numerous changes maybe made without straying from the scope of the present disclosure.

Preferred embodiments of the present disclosure are illustrated in thefigures with like numerals being used to refer to like and correspondingparts of the various drawings. It is also understood that terms such as“top”, “bottom”, “outward”, “inward”, and the like are words ofconvenience and are not to be construed as limiting terms. It is to benoted that the terms “first,” “second,” and the like, as used herein donot denote any order, quantity, or importance, but rather are used todistinguish one element from another. The terms “a” and “an” do notdenote a limitation of quantity, but rather denote the presence of atleast one of the referenced item. The modifier “about” used inconnection with a quantity is inclusive of the stated value and has themeaning dictated by the context (e.g., includes the degree of errorassociated with measurement of the particular quantity).

As used herein, the process of forming of a fluid mixture includesmixing a fluid with a powdered or particulate material, such asproppant, a powdered dissolvable or a hydratable additive (prior tohydration). The fluids are handled as continuous fluid streams over anuninterrupted episode for each fracture stage.

Referring to the drawings wherein, as previously stated, identicalreference numerals denote the same elements throughout the variousviews, FIG. 1 depicts in a simplified block diagram, elements of anapparatus 100 for preparing and delivering a continuous fluid mixture(slurry) of solids (proppant) and liquefied gas, including directproppant injection to a pressurized blender, or mixing apparatus,including sufficient fluid volume and proppant mass so as to achieve anuninterrupted episode for each individual fracture stage to achieve thedesired fracture stage design, according to an embodiment.

The apparatus 100 includes a proppant storage vessel 102 coupled to ahigh pressure differential solids feeder assembly 104 at an inlet 106 ofthe high pressure differential solids feeder assembly 104. The proppantstorage vessel 102 includes an outlet 108 configured in fluidiccommunication with the inlet 106 of the high pressure differentialsolids feeder assembly 104. The proppant storage vessel 102 isconfigured as a traditional unpressurized storage type vessel andincludes a body 110 configured to hold a proppant material 112 thereinat atmospheric pressure, also referred to herein as ambient pressure. Inan embodiment, the proppant storage vessel 102 may be configuredincluding an open top and configured to hold the proppant material 112therein at atmospheric pressure. In an embodiment, the proppant storagevessel may be configured including a closed top and configured to holdthe proppant material 112 therein at atmospheric pressure. The proppantstorage vessel 102 may further include a proppant material inlet 114coupled to a proppant material loading device 116 and a source ofproppant material (not shown). In an embodiment, the proppant material112 may be comprised of sand, ceramic proppant, a mixture thereof orother material utilized as proppant in hydraulic fracturing operations.The proppant storage vessel 102 provides adequate storage and loadingcapabilities to allow for a supply of proppant material 112 to the highpressure differential solids feeder assembly 104 sufficient to achievecontinuous operation of the apparatus 100 in an uninterrupted episodefor an individual fracture stage.

During operation, the proppant storage vessel 102 may be loaded by thematerial loading device 116, such as a screw auger, conveyor, or anyother means configured to move the proppant material 112 from a proppantsupply source (not shown) to the proppant storage vessel 102. Alternatemeans for providing the proppant material 112 to the proppant storagevessel 102 are anticipated herein. The proppant storage vessel 102 isconfigured to hold the proppant material 112 therein at atmosphericpressure and thus enables loading/recharging during operation of theremaining system components.

The high pressure differential solids feeder assembly 104 includes apump assembly capable of receiving a continuous proppant output flow 118at atmospheric pressure via outlet 108 of the proppant storage vessel102 and the inlet 106 of the high pressure differential solids feederassembly 104. The high pressure differential solids feeder assembly 104is further configured to provide at an outlet 120, a continuouspressurized proppant output flow 122 at a mixing pressure, wherein thecontinuous pressurized proppant output flow 122 is of a sufficient massflow to provide continuous operation of the apparatus 100 in anuninterrupted episode for each individual fracture stage. The mixingpressure at which the continuous pressurized proppant output flow 122 isdischarged is greater than the ambient pressure. In an embodiment, themixing pressure is in a range of about 50 psi to 400 psi, and preferablyat a pressure of approximately 300 psi.

A pressurized blender, or mixing apparatus, 124 is configured to receivethe continuous pressurized proppant output flow 122 via a proppant inlet126. A pressurized fracturing fluid storage vessel 128 is provided influidic communication via an outlet 130 with a fracturing fluid inlet132 of the pressurized mixing apparatus 124. The fracturing fluidstorage vessel 128 is configured for storage of a fracturing fluid 134at a required temperature and storage pressure, and more particularly ator above the mixing pressure. The pressurized mixing apparatus 124 isconfigured to receive a continuous pressurized fracturing fluid outputflow 136 at the mixing pressure via the inlet 132, wherein thecontinuous pressurized fracturing fluid output flow 136 is of asufficient volume to provide continuous operation of the apparatus 100in an uninterrupted episode for each individual fracture stage.

During operation, the continuous pressurized proppant output flow 122and the continuous pressurized fracturing fluid output flow 136 areblended, or mixed, within the pressurized mixing apparatus 124 at themixing pressure. Subsequent to mixing, the pressurized mixing apparatus124 provides a continuous fluid mixture output flow 138, previouslyreferred to herein as a slurry, to a high pressure fracturing fluid(slurry) pump assembly 142, via an outlet 140, wherein the continuousfluid mixture (slurry) output flow 138 is sufficient to providecontinuous operation of the apparatus 100 in an uninterrupted episodefor each individual fracture stage. In alternate embodiments, a fracturefluid (slurry) booster pump 141 may be provided inline between themixing apparatus 124 and the high pressure fracturing fluid (slurry)pump assembly 142, or alternatively provided as part of thefunctionality of the high pressure fracturing fluid (slurry) pumpassembly 142. The continuous fluid mixture (slurry) output flow 138 isoutput at the mixing pressure. The continuous fluid mixture (slurry)output flow 138 is received via a fluid mixture inlet 144 of the highpressure pump assembly 142. The high pressure fracturing fluid (slurry)pump assembly 142 is configured to deliver the continuous fluid mixture(slurry) output flow 138 received therein to a downstream component 146at an injection pressure, wherein the injection pressure is greater thanthe mixing pressure. More specifically, in an embodiment, the highpressure fracturing fluid (slurry) pump assembly 142 is configured todeliver a continuous high pressure fluid mixture (slurry) output flow148 via an outlet 150 of the high pressure fracturing fluid (slurry)pump assembly 142 to an inlet 152 of the downstream component 146, suchas a well head 154, wherein the continuous high pressure fluid mixture(slurry) output flow 148 is of sufficient volume and mass to providecontinuous operation of the apparatus 100 in an uninterrupted episodefor each individual fracture stage.

Referring more specifically to FIG. 2, illustrated is a portion of theapparatus 100 of FIG. 1 as indicated by dotted line in FIG. 1. Moreparticularly, illustrated in FIG. 2 are the high pressure differentialsolids feeder assembly 104 and the pressurized mixing apparatus 124. Theinclusion of the high pressure differential solids feeder assembly 104in apparatus 100 provides unlimited amounts of the proppant material 112to be continuously blended with the pressurized fracturing fluid 134,using conventional sand logistics and on-pad handling equipment. Thehigh pressure differential solids feeder assembly 104 is capable ofoperating continuously in uninterrupted episodes throughout eachfracture stage, in contrast to semi-batch operating modes of the stateof the art lock hoppers, whereby the proppant must be batch pressurizedin a mixing apparatus with multiple lock hopper cycles or multiple lockhopper configurations required to deliver sufficient output flow forsimilar desired fracture stage designs.

As illustrated in FIG. 2, the high pressure differential solids feederassembly 104 separates the low pressure inlet, and more particularly theinlet 106 from the high pressure outlet, and more particularly theoutlet 120. This separation enables transport of the bulk solids(proppant) from the low pressure inlet 106 to the high pressuredischarge area 120 on a continuous, uninterrupted basis whilesimultaneously preventing a flow of the pressurized fracturing fluid134, via the fracturing fluid output flow 136, back to the inlet 106. Incontrast to known lock hopper designs that may include a valveconfigured to intermittently open and close to create separation ofpressure zones, the high pressure differential solids feeder assembly104 provides for an uninterrupted solids flow at both the inlet 106 andthe outlet 120, simultaneously. In an embodiment, while some degree ofhigh pressure fluid backflow may occur through the high pressuredifferential solids feeder assembly 104, the device 104 is configured toactively manage such back flow (e.g., active venting).

In an embodiment, the high pressure differential solids feeder assembly104 may be a continuous solid feed pump assembly, such as a Posimetric®pump assembly, (described presently) that employs positive-displacementaction to provide precise flow control and positive metering of theunpressurized proppant material output flow 118 into the pressurizedmixing apparatus 124, a screw auger, conveyor, or any other similarmeans (described presently) configured to move the unpressurizedproppant material output flow 118 into the pressurized mixing apparatus124, an eductor pump assembly (described presently) that employs theVenturi effect to convert pressure energy of a motive fluid to velocityenergy to feed the unpressurized proppant material output flow 118 intothe pressurized mixing apparatus 124, or a rotary-type pump (i.e., arotary valve) that employs positive-displacement action to feed theunpressurized proppant material output flow 118 into the pressurizedmixing apparatus 124.

In an embodiment the pressurized mixing apparatus 140 is configured as atank that provides for mixing of contents therein in response toagitation or in response to static mixing utilizing plates and/or mixerelements that provide for mixing in response to turbulence and/or mixingof a plurality of flow paths generated in the flow.

In an embodiment, the integration of the high pressure differentialsolids feeder assembly 104 with the pressurized mixing apparatus 140 mayinclude coupling the outlet 120 of the high pressure differential solidsfeeder assembly 104 to a gas headspace (not shown) of the pressurizedmixer apparatus 140. In addition, in an embodiment, the pressurizedmixer apparatus 140 may employ a small retention volume so as to allowfor faster change-overs between proppant sizes and types.

Further embodiments of an apparatus for delivering a pressurized fluidusing continuous direct injection of a proppant at ambient pressure intoa pressurized mixing apparatus, of a sufficient volume and mass toprovide continuous operation of the apparatus 100 in an uninterruptedepisode for each individual fracture stage, are illustrated in FIGS.3-5. More particularly, illustrated are alternate embodiments of thehigh pressure differential solids feeder assembly 104 as described inFIGS. 1 and 2. Each of the embodiments of FIGS. 3-5 addresses the directdelivery of a dry proppant material, such as proppant material 112 ofFIG. 1, to a pump assembly for pressurization and subsequent mixing withthe fracturing fluid 134 in a pressurized mixing apparatus 124.Utilizing a dry proppant material obviates the need for additional fluidfor wetting, thereby simplifying the process and required equipment andremoving costly and potentially flammable (e.g., hydrocarbon) wettingagent(s). Each of the embodiments of FIGS. 3-5 describes a pump assemblythat may be utilized for the high pressure differential solids feederassembly 104, as described in FIGS. 1 and 2. Accordingly, like numbersare used to identify like elements throughout the described embodimentsand in an effort to provide a concise description of these embodiments,like features and elements previously described will not be furtherdescribed.

Referring more specifically to FIG. 3, illustrated is an embodiment ofan apparatus for delivering a continuous, uninterrupted fluid mixture,generally referenced 200. The apparatus 200 includes a proppant storagevessel 102 configured to contain therein an unpressurized proppantmaterial 112 and output a continuous unpressurized proppant output flow118 at ambient pressure. A high pressure differential solids feederassembly 104 is provided and coupled to the proppant storage vessel 102.The high pressure differential solids feeder assembly 104 includes aproppant inlet 106 in fluidic communication with the unpressurizedproppant storage vessel proppant output flow 118. In this particularembodiment, the high pressure differential solids feeder assembly 104 isa continuous solid feed pump assembly 202. The continuous solid feedpump assembly 202 employs positive-displacement action to feed theunpressurized proppant material output flow 118 without the need for apressurizing fluid, into the pressurized mixing apparatus as acontinuous flow sufficient to provide continuous operation of theapparatus 200 in an uninterrupted episode for each individual fracturestage. In this particular embodiment, the continuous solid feed pumpassembly 202 does not employ screws, augers, belts or vibratory trays toconvey the unpressurized proppant material output flow 118 and incontrast employs at least one vertical rotating spool 204 disposedwithin a pump body 208 to move the proppant material 112 therein. Thecontinuous proppant output flow 118 is initially input at an input 106that is coupled to the pump body 208. As the continuous proppant outputflow 118 enters and fills the pump assembly 202, and more particularlythe pump body 208, from above, the material locks itself firmly into theconfines of the rotating spool 204 contained therein, which carries itthrough an arc of approximately 180°. More particularly, the continuousproppant output flow 118 is rotated within the rotating spool 204,housed within the pump body 208, where it becomes “locked up” orcompacted so as to act as a solid mass, and discharged via an outputduct 210 at the outlet 120 as a continuous pressurized proppant outputflow 122 of sufficient mass to provide continuous operation of theapparatus 200 in an uninterrupted episode for each individual fracturestage. While within the pump body 208, the proppant material 118 acts asa solid mass and a seal against the high pressure outlet 120. At thetime of discharge via the outlet 120, the continuous pressurizedproppant material output flow 122 is output at an increased pressure,and more particularly at a mixing pressure that is higher than ambientpressure.

In a preferred embodiment, the continuous solid feed pump assembly 202is configured as a rotary displacement pump assembly 203, and includes aconsolidation section 212, a rotating section 214 and a dischargesection 216. During operation, the unpressurized proppant materialoutput flow 118 enters the pump assembly 202 and becomes consolidated asthe individual proppant material particles settle and come into contactwith each other as well as the sidewalls defining the pump body 208, theparticles become compacted and act as a solid mass and form a sealagainst the high pressure outlet environment. As the unpressurizedproppant material output flow 118 rotates in the rotating spool 204 andpump body 208, the pressure of the proppant material output flow 118 isincreased, forming the continuous pressurized proppant output flow 122.Discharge of the continuous pressurized proppant output flow 122 at theincreased mixing pressure occurs upon rotating of the rotating spool 204to the outlet 120. Exemplary pump assemblies are described in commonlyassigned U.S. Pat. No. 8,006,827, D. Aldred et al., “TransportingParticulate Material”, issued Aug. 3, 2011, which is incorporated byreference herein in its entirety.

The continuous solid feed pump assembly 202 is configured to output thecontinuous pressurized proppant output flow 122 at the mixing pressure,wherein the mixing pressure is greater than the ambient pressure. Theapparatus 200 further includes a fracturing fluid storage vessel 128configured to contain therein a fracturing fluid 134 and output acontinuous pressurized fracturing fluid output flow 136 at or above themixing pressure, of a sufficient volume to provide continuous operationof the apparatus 200 in an uninterrupted episode for each individualfracture stage. A pressurized blender, or mixing apparatus, 124 iscoupled to the continuous solid feed pump assembly 202 to receive thedischarged continuous pressurized proppant output flow 122. Thepressurized mixing apparatus 124 is additionally coupled to thepressurized fracturing fluid storage vessel 128 to receive thedischarged continuous fracturing fluid output flow 136 therefrom. Themixing apparatus 124 is configured to mix the continuous pressurizedproppant output flow 122 and the continuous pressurized fracturing fluidoutput flow 136 therein and output a continuous output of a fluidmixture (slurry) 138 of proppant and fracturing fluid, at the mixingpressure, and of a sufficient volume and mass to provide continuousoperation of the apparatus 200 in an uninterrupted episode for eachindividual fracture stage to deliver the proppant mass and fluid volumedesired by the fracture stage design. A fracturing fluid (slurry)booster pump 141 and a high pressure fracturing fluid (slurry) pumpassembly 142 are coupled to the mixing apparatus 124 and configured toreceive the continuous output of a fluid mixture (slurry) 138 anddeliver a continuous flow of a high pressure fluid mixture (slurry) 148therein to a downstream component 146 at an injection pressure and in anamount sufficient to provide continuous operation of the apparatus 200in an uninterrupted episode for each individual fracture stage. Theinjection pressure of the continuous flow of a high pressure fluidmixture (slurry) 148 is at or greater than the mixing pressure.

Referring more specifically to FIG. 4, illustrated is another embodimentof an apparatus 300 for delivering a continuous flow of a high pressurefluid mixture (slurry) of a sufficient volume and mass to providecontinuous operation of the apparatus 300 in an uninterrupted episodefor each individual fracture stage as desired by the fracture stagedesign. The apparatus 300 includes a proppant storage vessel 102configured to contain therein a proppant material 112 and output acontinuous proppant output flow 118 at ambient pressure. The apparatus300 further includes a fracturing fluid storage vessel 128 configured tocontain therein a pressurized fracturing fluid 134 and output acontinuous pressurized fracturing fluid output flow 136 at or above amixing pressure, wherein the mixing pressure is greater than the ambientpressure as previously described. A high pressure differential solidsfeeder assembly 104 is provided and coupled to the proppant storagevessel 102 and the fracturing fluid storage vessel 128. The highpressure differential solids feeder assembly 104 includes a proppantinlet 106 in fluidic communication with the proppant storage vesselcontinuous proppant output flow 118 and a fracture fluid inlet 324 influidic communication with at least a portion of the continuouspressurized fracturing fluid output flow 136. In this particularembodiment, the high pressure differential solids feeder assembly 104 isan eductor pump assembly 302. During operation, the eductor pumpassembly 302 employs the Venturi effect of a converging-diverging nozzleto convert the pressure energy of a motive fluid, and more particularlya portion of the continuous fracturing fluid output flow 136, tovelocity energy to feed the proppant material 112. Similar to thepreviously described continuous solid feed pump assembly 202, theeductor pump assembly 302 does not employ screws, augers, belts orvibratory trays to convey the proppant material 112 within the pumpassembly toward the downstream components.

As illustrated in FIG. 4, the continuous proppant output flow 118 isinitially input into the eductor pump assembly 302 via an input duct 306that is coupled to a pump body 308. The input of the continuous proppantoutput flow 118 may be metered by a valve mechanism (not shown) disposedin the input duct 306. In an embodiment, the eductor pump assembly 302further includes a first converging nozzle 310, a second convergingnozzle 312, a mixing chamber 314 and a diffuser, or expansion feature,316.

In an embodiment, the eductor pump assembly 302 includes the eductorbody 308, and more particularly a suction chamber 318 that is driven bythe motive fluid, and more particularly at least a portion of thecontinuous fracturing fluid output flow 136 utilized as a motive flow.In an embodiment, at least a portion of the continuous fracturing fluidoutput flow 136 is input directly into the pressurized mixing apparatus124. The continuous fracturing fluid output flow 136 is acceleratedthrough the first converging nozzle 310. As with traditional eductors,accelerating a higher pressure fluid through the first converging nozzle310 drops the static pressure of a motive flow exiting through the firstconverging nozzle 310, while simultaneously decreasing the staticpressure within the suction chamber 318. The lower suction pressure inthe suction chamber 318 draws in the continuous proppant output flow118, as a suction flow via the inlet port 106 of the eductor pumpassembly 302. Subsequently, a continuous flow of a fluid mixture 320 ofa sufficient volume and mass to provide continuous operation of theapparatus 300 in an uninterrupted episode for each individual fracturestage, comprised of a combination of the continuous proppant output flow118 and the continuous pressurized fracturing fluid output flow 136, isdelivered to the second converging nozzle 312 prior to reaching themixing chamber 314. The fluid mixture 320, comprised of the continuousproppant output flow 118 and the continuous pressurized fracturing fluidoutput flow 136, is further mixed within the pressurized mixing chamber314 as the stratifications between the two fluids are allowed to settleout and as the turbulent fluid structure is reduced. The continuous flowof the fluid mixture 320 exiting the mixing chamber 314 is expanded inthe expansion feature 316, prior to being delivered to the downstreamcomponents that may ultimately be in fluidic communication with awellhead. The expansion feature 316 provides an expansion of the fluidmixture 320 and provides a decrease in the velocity of the fluid mixture320 and recovery of the pressure of the fluid mixture 320 allowing thefluid to be delivered to a pressurized mixing apparatus 124 in acontinuous flow, at the mixing pressure, and a sufficient volume andmass to provide continuous operation of the apparatus 300 in anuninterrupted episode for each individual fracture stage to deliver theproppant mass & fluid volume desired by the fracture stage design.

During operation of the apparatus 300, including the eductor pumpassembly 302, the eductor pump assembly 302 is placed in operation bypressurizing the suction chamber 318. Subsequent to the appropriatepressure condition being reached, an optional valve mechanism, or gate,322, disposed between the proppant storage vessel 102 and the inlet port106 may be opened to allow the proppant storage vessel 102 contents toenter the eductor pump assembly 302, and more particularly the suctionchamber 318. The suction chamber 318 draws in the continuous proppantoutput flow 118, including the proppant material 112, as the suctionflow, and subsequently mixes with the motive flow, and moreparticularly, at least a portion of the pressurized fracturing fluidoutput flow 136. Operation of the apparatus is continuous anduninterrupted with a continuous flow of the proppant output flow 118 andthe fracturing fluid output flow 136 in a volume sufficient to providecontinuous operation of the apparatus 300 in an uninterrupted episodefor each individual fracture stage as desired by the fracture stageplan.

It should be noted that valve mechanism 322 is optional, being requiredin an application where the desire is to allow the eductor pump assembly302 to remain at full pressure. As valves in the direct path of theproppant output flow 118, and more particularly proppant material 112,it will be subject to a harsh abrasive environment, it is realized thatvalve mechanism 322 will be subject to higher wear rates. As such, anembodiment eliminating the valve mechanism 322 is anticipated.

The eductor pump assembly 302 is configured to output a continuouspressurized proppant output flow 122 of a sufficient mass and acontinuous pressurized fracturing fluid output flow 136 of a sufficientvolume to provide continuous operation of the apparatus 300 in anuninterrupted episode for each individual fracture stage. The apparatus300 further includes the pressurized blender, or pressurized mixingapparatus, 124 coupled to the eductor pump assembly 302 to continuouslyreceive the discharged continuous pressurized proppant output flow 122therefrom and the continuous pressurized fracturing fluid output flow136. The pressurized mixing apparatus 124 is configured to mix thecontinuous pressurized proppant output flow 122 and the continuouspressurized fracturing fluid output flow 136 therein and output acontinuous pressurized fluid mixture (slurry) output flow 138 ofproppant and fracturing fluid at the mixing pressure. A fracturing fluidbooster pump 141 and a high pressure fracturing fluid (slurry) pumpassembly 142 are coupled to the mixing apparatus 124 and configured todeliver the continuous pressurized fluid mixture (slurry) 138 therein toa downstream component 146 as a high pressure fluid mixture (slurry)output flow 148 at an injection pressure, wherein the injection pressureis greater than the mixing pressure, and of a sufficient volume and massto provide continuous operation of the apparatus 300 in an uninterruptedepisode for each individual fracture stage to deliver the proppant mass& fluid volume desired by the fracture stage plan.

Accordingly, the inclusion of the eductor pump assembly 302, asdescribed in apparatus 300, provides for use of at least a portion ofthe continuous flow of pressured fracturing fluid 136 as the motivefluid flow through the eductor pump assembly 302 to convey the proppant112 and more particularly the proppant output flow 118 into the flowingmotive fluid.

Referring now to FIG. 5, illustrated is another embodiment of anapparatus for preparing and delivering a continuous fluid mixture(slurry) of solids (proppant) and liquefied gas, generally referenced400. The apparatus 400 includes a proppant storage vessel 102 configuredto contain therein a proppant material 112 and output a continuousproppant output flow 118 at ambient pressure. The apparatus 400 furtherincludes a fracturing fluid storage vessel 128 configured to containtherein a pressurized fracturing fluid 134 and output a continuouspressurized fracturing fluid output flow 136 at or above a mixingpressure, wherein the mixing pressure is greater than the ambientpressure as previously described. A high pressure differential solidsfeeder assembly 104 is provided and coupled to the proppant storagevessel 102 and the fracturing fluid storage vessel 128. The highpressure differential solids feeder assembly 104 includes a proppantinlet 106 in fluidic communication with the continuous proppant storagevessel proppant output flow 118. In this particular embodiment, the highpressure differential solids feeder assembly 104 is a positivedisplacement pump, and more particularly a rotary-type positivedisplacement pump, such as an internal gear, screw, rotary valve, orauger type pump assembly, referenced 402. The unique design of thepositive displacement pump 402 ensures that the proppant material 112 isconstantly present at a feed inlet 404, while the controlled rotation ofa feed mechanism 406 moves the proppant material 112, and moreparticularly the continuous unpressurized proppant output flow 118, fromthe ambient pressure feed inlet 404 to a pressurized discharge point408. In the illustrated embodiment, the feed mechanism 406 comprises ascrew mechanism 410 (a helical surface surrounding a central cylindricalshaft) disposed inside a hollow body 412.

As illustrated in FIG. 5, the continuous proppant output flow 118 isinitially input into the rotary-type positive displacement pump 402 viathe feed inlet 404. Similar to the previous embodiment, the input of thecontinuous proppant output flow 118 may be metered by an optional valvemechanism (not shown). Similar to the continuous solid feed pumpassembly 202 of FIG. 3, the positive displacement pump assembly 402employs positive-displacement action to feed the proppant material 112as a free-flowing material with a uniform discharge in a linearvolumetric fashion. In contrast to the continuous solid feed pumpassembly 202 of FIG. 3, the positive displacement pump assembly 402employs screws, augers, rotary valves, belts or vibratory trays toconvey the proppant material 112 therein. The continuous proppant outputflow 118 is initially input at the feed inlet 404 that is coupled to thepump body 412. As the continuous proppant output flow 118 enters andfills the pump assembly 402, and more particularly the pump body 412,the material is carried by the feed mechanism 406 contained therein,toward the discharge point 408. The continuous ambient pressure proppantoutput flow 118 is rotated within the feed mechanism 406, housed withinthe pump body 412 and discharged via an output duct 414 at the dischargepoint 408 as a continuous pressurized proppant output flow 122. At thetime of discharge via an outlet 120, the continuous proppant materialoutput flow 122 is output at an increased pressure, and moreparticularly at a mixing pressure that is greater than the ambientpressure and of a sufficient mass to provide continuous operation of theapparatus 400 in an uninterrupted episode for each individual fracturestage to deliver the proppant mass & fluid volume desired by thefracture stage plan.

In a preferred embodiment, during operation, the proppant material 112enters the rotary-type positive displacement pump 402 at the feed inlet404. As the proppant material 112 rotates in the feed mechanism 410 andpump body 412, the pressure of the proppant material 112 is increased.Discharge of the proppant material 112 at the increased mixing pressureoccurs upon rotation of the feed mechanism 406 relative to the outlet120.

The apparatus 400 further includes a pressurized blender, or mixingapparatus, 124 coupled to the rotary-type positive displacement pump 402to receive the discharged continuous pressurized proppant output flow122 therefrom and the continuous pressurized fracturing fluid outputflow 136. The mixing apparatus 124 is configured to mix the continuouspressurized proppant output flow 122 and the continuous pressurizedfracturing fluid output flow 134 therein and output a continuouspressurized flow of a fluid mixture (slurry) 138 of proppant material112 and fracturing fluid 134 at an increased pressure of a sufficientvolume and mass to provide continuous operation of the apparatus 400 inan uninterrupted episode for each individual fracture stage as requiredby the fracture stage design. A high pressure fracturing fluid (slurry)pump assembly 142 coupled to the mixing chamber 124 is configured toreceive the continuous pressurized flow of a fluid mixture (slurry) 138and deliver a continuous pressurized flow of a high pressure fluidmixture (slurry) 148 to a downstream component 146 at an injectionpressure, wherein the injection pressure is greater than the mixingpressure, and of a sufficient volume and mass to provide continuousoperation of the apparatus 400 in an uninterrupted episode for eachindividual fracture stage. In this particular embodiment, a separatebooster pump is not provided, and in lieu of, boosting of the mixingpressure is provided as part of the functionality of the high pressurefracturing fluid (slurry) pump assembly 142.

FIG. 6 is a schematic block diagram of a method 500 of delivering afluid mixture using direct proppant injection to a pressurized mixingapparatus including the high pressure differential solids feederassembly 100, 200, 300, 400 according to an embodiment disclosed herein.Generally, the method involves providing an input of a proppant material112 to an ambient pressure proppant storage vessel 102, and providing aninput of a pressurized fracturing fluid 134 to a fracture fluid storagevessel 128, at a step 502. Next in step 504, a continuous proppantoutput flow 118 at ambient pressure from the proppant storage vessel 102is input into a high pressure differential solids feeder assembly 104.As previously described, the high pressure differential solids feederassembly 104 may be configured as a positive displacement pump assembly,and more particularly a continuous solid feed pump assembly 202 (as bestillustrated in FIG. 3), as an eductor pump assembly 302 (as bestillustrated in FIG. 4) or a rotary-type positive displacement pump 402(as best illustrated in FIG. 5). Next in step 506, a continuouspressurized proppant output flow 122 and a continuous pressurizedfracturing fluid output flow 136 are input to a pressurized mixingapparatus 124. The pressurized mixing apparatus 124 is configured to mixthe continuous pressurized proppant output flow 122 and the continuouspressurized fracturing fluid output flow 136 therein and output acontinuous pressurized fluid mixture (slurry) output flow 138 of theproppant and fracturing fluid at the mixing pressure, at step 508. Thepressure of the continuous pressurized fluid mixture (slurry) outputflow 138 is next increased in a high pressure fracturing fluid (slurry)pump assembly 142, at step 510. Subsequently a continuous high pressurefluid mixture (slurry) 148 is delivered to one or more downstreamcomponents 146, at a step 512, and ultimately may include delivery to awell head.

The apparatus for delivering a fluid using direct proppant injection, asdisclosed herein, enables continuous operation of the apparatus at asteady condition in an uninterrupted episode for each individualfracture stage to deliver the proppant mass & fluid volume desired bythe fracture stage design. The apparatus by providing continuouspressurized flows of proppant and fracturing fluid into the mixingapparatus eliminates the stop-start operation that must be performedwhen the volume being held is smaller than the desired amount needed foreach individual fracture stage design. The apparatus removes therequirement to store all (or at least a significant portion) of theproppant to be used for each fracturing stage in a pressurized bulkproppant storage pressure vessel, and instead allows use of existingproppant management apparatus at ambient pressure such that an unlimitedamount of proppant can be blended online (as opposed to in batches) withthe pressurized fracturing fluid to deliver the proppant mass and fluidvolume desired by the fracture stage design.

Additional commercial advantages of the disclosed apparatus are relatedto the current problem faced in unconventional gas development and therequirement to mix/blend chemicals and a proppant, namely sand withfracturing fluids (e.g., liquid CO₂, liquid propane gas) that requirethey always be contained at a suitable mixing pressure to avoidvaporization of these fracturing fluids. Accordingly, disclosed is anapparatus and method of continuously preparing and delivering a fluidmixture of solids (proppant) with liquefied gas using a high pressuredifferential solids feeder assembly and direct proppant injection into apressurized mixing apparatus in such a way that a continuous pressurizedflow of proppant of a sufficient volume to provide continuous operationof the apparatus in an uninterrupted episode for each individualfracture stage can be provided without being constrained by the totalvolume limits of the known lock hopper based approaches. The disclosedapparatus provides a continuous pressurized fluid mixture output flow ofa sufficient volume and mass to provide continuous operation of theapparatus in an uninterrupted episode for each individual fracture stageto deliver the proppant mass and fluid volume desired by the fracturestage design.

The foregoing has described an apparatus and method of preparing anddelivering a fluid mixture (slurry) of solids (proppant) and liquefiedgas using direct injection of a proppant into a pressurized mixingapparatus. While the present disclosure has been described with respectto a limited number of embodiments, those skilled in the art, havingbenefit of this disclosure, will appreciate that other embodiments maybe devised which do not depart from the scope of the disclosure asdescribed herein. While the present disclosure has been described withreference to exemplary embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe disclosure. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out the disclosure. It is, therefore, to be understood that theappended claims are intended to cover all such modifications and changesas fall within the true spirit of the disclosure.

1. An apparatus for preparing and delivering a fluid mixture comprising:a high pressure differential solids feeder assembly coupled to aproppant storage vessel at an ambient pressure, the high pressuredifferential solids feeder assembly including a proppant inlet influidic communication with a proppant flow at the ambient pressure, thehigh pressure differential solids feeder assembly configured to output acontinuous pressurized proppant output flow of a sufficient mass toachieve continuous operation of the apparatus in an uninterruptedepisode for an individual fracture stage, wherein the continuouspressurized proppant output flow is output at a mixing pressure, whereinthe mixing pressure is greater than the ambient pressure; and apressurized mixing apparatus coupled to the high pressure differentialsolids feeder assembly, the pressurized mixing apparatus including atleast one inlet in fluidic communication with the continuous pressurizedproppant output flow and a continuous pressurized fracturing fluid flow,the pressurized mixing apparatus configured to mix the continuouspressurized proppant output flow and the continuous pressurizedfracturing fluid flow therein and output a continuous flow of apressurized fluid mixture of proppant and fracturing fluid of asufficient volume and mass to achieve continuous operation of theapparatus in an uninterrupted episode for the individual fracture stage,wherein the continuous flow of the pressurized fluid mixture of proppantand fracturing fluid is output at or above the mixing pressure.
 2. Theapparatus of claim 1, further comprising: a pump assembly coupled to thepressurized mixing chamber and configured to deliver the continuous flowof the pressurized fluid mixture of proppant and fracturing fluid to adownstream component at an injection pressure, wherein the injectionpressure is greater than the mixing pressure.
 3. The apparatus of claim1, wherein the high pressure differential solids feeder assembly is arotary displacement pump assembly with a consolidation section, arotation section and a discharge section.
 4. The apparatus of claim 1,wherein the high pressure differential solids feeder assembly is aneductor pump assembly.
 5. The apparatus of claim 1, wherein the highpressure differential solids feeder assembly is a rotary positivedisplacement pump assembly.
 6. The apparatus of claim 1, wherein themixing pressure is in a range of 200-400 psi.
 7. The apparatus of claim5, wherein the mixing pressure is approximately 300 psi.
 8. Theapparatus of claim 1, wherein the injection pressure is in a range of5000-12,000 psi or higher.
 9. The apparatus of claim 1, wherein theinjection pressure is approximately 10,000 psi.
 10. The apparatus ofclaim 1, wherein the proppant material is one of sand, ceramic proppant,or a mixture thereof.
 11. The apparatus of claim 1, wherein thefracturing fluid is one of liquid CO₂, liquid propane or a mixturethereof.
 12. An apparatus for preparing and delivering a fluid mixturecomprising: a proppant storage vessel configured to contain therein aproppant material and output a proppant output flow at ambient pressure;a high pressure differential solids feeder assembly coupled to theproppant storage vessel, the high pressure differential solids feederassembly including a proppant inlet in fluidic communication with theproppant output flow, the high pressure differential solids feederassembly configured to output a continuous pressurized proppant outputflow of a sufficient mass to achieve continuous operation of theapparatus in an uninterrupted episode for an individual fracture stage,wherein the continuous pressurized proppant output flow is output at amixing pressure, wherein the mixing pressure is greater than the ambientpressure; a fracturing fluid storage vessel configured to containtherein a fracturing fluid and output a continuous pressurizedfracturing fluid output flow at a mixing pressure, wherein the fracturemixing pressure is greater than the ambient pressure; a pressurizedmixing apparatus coupled to the high pressure differential solids feederassembly, the pressurized mixing apparatus including at least one inletin fluidic communication with the continuous pressurized proppant outputflow and the continuous pressurized fracturing fluid flow, thepressurized mixing apparatus configured to mix the continuouspressurized proppant output flow and the continuous pressurizedfracturing fluid flow therein and output a continuous flow of apressurized fluid mixture of proppant and fracturing fluid of asufficient volume and mass to achieve continuous operation of theapparatus in an uninterrupted episode for the individual fracture stage,wherein the continuous flow of the pressurized fluid mixture of proppantand fracturing fluid is output at or above the mixing pressure; and apump assembly coupled to the pressurized mixing chamber and configuredto deliver the pressurized fluid mixture therein to a downstreamcomponent at an injection pressure, wherein the injection pressure isgreater than the mixing pressure.
 13. The apparatus of claim 12, whereinthe mixing pressure is in a range of 200-400 psi.
 14. The apparatus ofclaim 13, wherein the mixing pressure is approximately 300 psi.
 15. Theapparatus of claim 12, wherein the injection pressure is in a range of5000-12,000 psi.
 16. The apparatus of claim 12, wherein the proppantmaterial is one of sand, ceramic proppant, or a mixture thereof, and thefracturing fluid is one of liquid CO₂, liquid propane or a mixturethereof.
 17. The apparatus of claim 12, wherein the high pressuredifferential solids feeder assembly is coupled to the proppant storagevessel, the high pressure differential solids feeder assemblycomprising: a consolidation section configured to cause the proppantmaterial to compact and act as a solid mass; a rotating sectionconfigured to increase the pressure of the proppant material therein;and a discharge section configured to discharge the proppant material atthe increased mixing pressure.
 18. The apparatus of claim 12, whereinthe high pressure differential solids feeder assembly is an eductor pumpassembly coupled to the proppant storage vessel and the fracturing fluidstorage vessel, the eductor pump assembly comprising: a suction chamberin fluidic communication with the proppant output flow, the fracturefluid output flow and a motive fluid flow, the suction chamberconfigured to output a fluid mixture to a mixing chamber; and anexpansion feature coupled to the mixing chamber and configured to expandthe fluid mixture therein for delivery to a downstream component. 19.The apparatus of claim 12, wherein the high pressure differential solidsfeeder assembly is rotary positive displacement pump assembly coupled tothe proppant storage vessel, the rotary positive displacement pumpassembly comprising: a pump body, including a feed inlet at a first endand a discharge point at a second end; and a feed mechanism disposedwithin the pump body and configured to move the proppant material fromthe feed inlet to the discharge point while increasing a pressure of theproppant material from an ambient pressure to the mixing pressure.
 20. Amethod of preparing and delivering a fluid mixture, comprising:providing a continuous proppant output flow at ambient pressure into ahigh pressure differential solids feeder assembly configured to output acontinuous pressurized proppant output flow of a sufficient mass toachieve continuous operation of an apparatus in an uninterrupted episodefor an individual fracture stage, wherein the continuous pressurizedproppant output flow is output at a mixing pressure, wherein the mixingpressure is greater than the ambient pressure; inputting the continuouspressurized proppant output flow and a continuous pressurized fracturefluid output flow at the mixing pressure and of a sufficient volume toachieve continuous operation of the apparatus in an uninterruptedepisode for an individual fracture stage, into a pressurized mixingapparatus; and mixing the continuous pressurized proppant output flowand the continuous pressurized fracturing fluid output flow therein thepressurized mixing apparatus and outputting a continuous pressurizedflow of a fluid mixture of proppant and fracturing fluid of a sufficientvolume and mass to achieve continuous operation of the apparatus in anuninterrupted episode for the individual fracture stage, wherein thecontinuous flow of the pressurized fluid mixture of proppant andfracturing fluid is output at or above the mixing pressure.
 21. Themethod of delivering a fluid mixture of claim 20, further comprising:providing an input of a proppant material at ambient pressure to aproppant storage vessel, the proppant storage vessel configured tooutput the continuous proppant output flow at ambient pressure; andproviding an input of a fracture fluid at a mixing pressure to afracture fluid storage vessel, the fracture fluid storage vesselconfigured to output the continuous pressurized fracture fluid outputflow at the mixing pressure.
 22. The method of delivering a fluidmixture of claim 20, further comprising: increasing the pressure of thecontinuous flow of the pressurized fluid mixture of proppant andfracturing fluid in a pump to output a continuous pressurized flow of anincreased pressure fluid mixture; and delivering the continuouspressurized flow of an increased pressure fluid mixture to one or moredownstream components.